Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(a) Doppler effect: according to the Doppler effect, the phase change Δθ(t) of the reflected signal is proportional to motion of the measured location, scaled by wavelength of the signal Δθ(t)= 4πΔx(t)/λ, where Δx(t) is the chest displacement and λ is the wavelength of the transmitted signal; (b) Standing wave: the figure shows a possible sinusoidal standing wave. The different lines show the standing wave at different moments in time.
